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prefixed_writer.go
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/
prefixed_writer.go
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package gexec
import (
"bytes"
"io"
"sync"
)
/*
PrefixedWriter wraps an io.Writer, emiting the passed in prefix at the beginning of each new line.
This can be useful when running multiple gexec.Sessions concurrently - you can prefix the log output of each
session by passing in a PrefixedWriter:
gexec.Start(cmd, NewPrefixedWriter("[my-cmd] ", GinkgoWriter), NewPrefixedWriter("[my-cmd] ", GinkgoWriter))
*/
type PrefixedWriter struct {
prefix []byte
writer io.Writer
lock *sync.Mutex
isNewLine bool
isFirstWrite bool
}
func NewPrefixedWriter(prefix string, writer io.Writer) *PrefixedWriter {
return &PrefixedWriter{
prefix: []byte(prefix),
writer: writer,
lock: &sync.Mutex{},
isFirstWrite: true,
}
}
func (w *PrefixedWriter) Write(b []byte) (int, error) {
w.lock.Lock()
defer w.lock.Unlock()
newLine := []byte("\n")
segments := bytes.Split(b, newLine)
if len(segments) != 0 {
toWrite := []byte{}
if w.isFirstWrite {
toWrite = append(toWrite, w.prefix...)
toWrite = append(toWrite, segments[0]...)
w.isFirstWrite = false
} else if w.isNewLine {
toWrite = append(toWrite, newLine...)
toWrite = append(toWrite, w.prefix...)
toWrite = append(toWrite, segments[0]...)
} else {
toWrite = append(toWrite, segments[0]...)
}
for i := 1; i < len(segments)-1; i++ {
toWrite = append(toWrite, newLine...)
toWrite = append(toWrite, w.prefix...)
toWrite = append(toWrite, segments[i]...)
}
if len(segments) > 1 {
lastSegment := segments[len(segments)-1]
if len(lastSegment) == 0 {
w.isNewLine = true
} else {
toWrite = append(toWrite, newLine...)
toWrite = append(toWrite, w.prefix...)
toWrite = append(toWrite, lastSegment...)
w.isNewLine = false
}
}
_, err := w.writer.Write(toWrite)
if err != nil {
return 0, err
}
}
return len(b), nil
}